In accordance with the recent development of an ultra-large scale integrated circuit, a developed technique and an electron beam exposure system are used for the purpose of forming very fine patterns. This electron beam exposure apparatus can form very fine patterns as disclosed in many publications such as, for example, H. C. Pfeiffer, "Variable Spot Shaping for Electron-beam Lithography", J. Vac. Sci. Technol., 15(3), May/June, 1978, pages 887 through 890. However, in the electron beam lithographic process disclosed in this publication exposure of the pattern cannot be carried out at high speed; therefore, such electron beam lithography exhibits some problems during practical use.
For removing the drawbacks of the conventional system, a new apparatus as will be described hereinafter was developed. In this new apparatus, exposure of the pattern is carried out by using an electron beam having a rectangular section which can be varied in accordance with the form of the pattern to be exposed. This new apparatus was disclosed in many articles such as, for example, T. H. P. Chang et al, "Scanning Electron Beam Lithography for Fabrication of Magnetic Bubble Circuits", IBM Journal of Research and Development, Vol. 20, No. 4, July, 1976, pages 376 through 388.
Usually, the electron beam exposure apparatus is controlled by a central processing unit, and the data of numerous patterns are used in the electron beam exposure apparatus. For example, about one million rectangular patterns are required for exposing a large scale integrated circuit (LS1) by using an electron beam exposure apparatus which uses an electron beam having a rectangular section, and the data corresponding to one pattern include the data of the position (coordinate of an initial point) (X.sub.1, Y.sub.1) and of the dimension (size of the pattern) (X.sub.2, Y.sub.2). Such data can be derived from binary information, for example, a digital number with 16 bits, therefore, information corresponding to one pattern is composed of 64 bits, and the information corresponding to one million patterns is composed of 64 megabits. A preferable exposing speed of a conventionally used electron beam exposure apparatus is one chip per second, that is, one million patterns per second, therefore, the data transfer speed of the apparatus is 64 megabits per second. Such pattern data are stored in a suitable memory and read out in accordance with a command of the central processing unit. The transfer speed of 64 megabits per second can only be realized by using a very high speed memory such as that used in a large scale electronic computer. The magnetic disc, which has a large capacity and which is widely used in the election beam exposure system, cannot be used due to the fact that the memory of the magnetic disc cannot be operated at such a high speed. Further, utilization of an electronic computer having a large capacity, high speed semiconductor memory in electron beam lithography is not economical.